Yes, it's mere temperature...or warmth. The pliant new growth is tender and so, like most things, it bends when warm. That's part of it. The other aspect is that warm sun strikes the leaves before the root-zone has warmed up and so the plant isn't effectively drawing moisture up from the roots yet. I would advise a more porous mix for citrus. Miracle Grow will compact and lead to lack of oxygen in the root-zone eventually. I'd re-pot as soon as the current new growth has become stiff (and before the next flush of growth commences). As always, whenever you suspect something amiss or unusual, closely inspect your plants for signs of pest. Josh

Could be a couple of things, but on my lime trees, when I've had this problem,it turned out to be spider mites. Look closely and see if you see any of the leaves kind of stuck together, with a little webbing. They basically suck the juices out of the leaves. Just treat with an insecticidal soap, and it usually clears up pretty quick. Sometimes too much water will yellow the leaves...might need fert.....just my 2 cents.

Is the side that's dying the same side that has the patches of bark missing? If so, that's what's causing the dying leaves. It looks like the bark is missing all the way around one of those main branches (called 'girdling') which will kill the branch as no water or nutrients can get up to the leaves at that point. Like a tourniquet on an arm, the blood can't flow. (kind of) If that's the case the question becomes, what caused the girdling? To me it looks possible like something gnawed away the bark. Are there critters in your area that could do that? Scale won't cause that kind of damage.

I have a few trees with leaves like that too. I just thought it was the extreme heat in summer, changing light levels as we go into fall and a few nights now that the night temperatures got to the mid 30s and jumped up fast during the day. Maybe the cooler roots were not able to keep up as the sun hits their leaves as they are in full sun? Some of my trees are in black plastic pots, but I have been changing them out to light tan or light grey when they need repotting. I will check to see if maybe the black potted trees are showing more signs of stress or nutrient deficiency. My Dekopons/Shiranui showed stress this summer and so did the Owaris which look much better with the cooler weather. The Dekopons were my easiest trees other years. This year they do not even have fruit, but maybe they are alternate bearers? Their leaves have shown a deficiency since late summer but I am not sure what it is. I thought it was more related to heat stress as the newer leaves are beginnig to look ok. The other trees showing problems are the Meyer Lemon and the Persian Lime. They always seem to need a slightly higher dose of fertilizer and there were times I didn't get to fertilizer the trees as regularly this summer as I had the house shingles repaired and painted which took most of the summer and my trees were often in the way of the workmen. I'll take a better look tomorrow morning to see if there are any others. I was not really that concerned thinking it was the change of season here and all these trees seem to be the ones known to be most affected by changing light levels and temperature. I was thinking about bringing them back into the greenhouse and leaving the others outside for a while yet. Next week is supposed to get warmer again so I might leave them all out another week or so. You all seem to fertilize at a much higher rate than I do. I use 1 tsp. per gallon of water (per the label) vs the 1 tablespoon many of you use. The most FP I use is 1-1/2 tsp for the Meyer Lemon and my limes as they seem to need more. I try to fertilize every time they need water. I do not water them first before I water either, so maybe that is why your trees can take the higher dose of FP without burning the roots. I don't fertilize first if the media is bone dry though. Everyone's trees sure look nice and green and shiny compared to mine. Mine have been recovering from my greenhouse overheating in April so I thought that may be why I was seeing some stress or deficiencies too. I have been thinking maybe I should increase my FP dosage rate to get that look, but I was afraid to try that as they have been in the recovery stage. I do supplement with the Osmocote Plus for times I can't regularly feed with FP and also with Fish/Kelp foliar feeds. I usually do not feed any of my plants in the low light months of late December thru early March but if they look like they need it I only feed at a greatly reduced rate. I have been using Repti-Bark for two years I think. It is 100% fir bark. I had previously been using pine bark fines but it was harder for me to get it than the Repti-bark. I will check tomorrow if there seems to be a correlation with the type of bark. It might break down differently than pine bark and that might affect the pH? I will also check the pH of the different 511 potting mixes. I have been busy so I have not spent as much time looking at them this week. Most are in the midst of a huge growth and blooming spurt though. I thought that maybe this is a result of the overheat stress in April and the hot summer we had. They are finally more full of baby fruit than they had all summer, probably because the roots have finally recovered and now the tree can grow leaves, flowers and fruit. I hope you can figure out what is causing the stress your trees leaves are showing. I think it takes a lot of close observation to figure it out. I find it is very hard to tell by the pictures which deficiency the tree has at first, but once you determine it you know it the next time you see it again. It seems though that the problem is probably related to an environmental problem if you are using the FP which has all the Macro and Micronutrients citrus trees need. Having grown orchids for years I have found sometimes just moving a plant a few inches causes the plants to flourish. It could be the same with citrus trees. Some seem to need just a bit more shade or sun, warmth or coolness, air movement, etc. If you do have a problem tree, as Mike says, quarantine it just in case it has a virus, fungal problem or insect infestation that you haven't discovered yet. You don't want the problem to spread throughout your collection, especially as your trees will be more stressed when they come inside and are grown in overcrowded conditions. Without the outdoor natural predictors, the insect population can explode in a greenhouse and grow room. Without the cleansing rains and constant natural air movement, fungal and virus can also explode indoors. Cory